Abstract: The invention relates to a novel process for the anionic polymerization of lactams, in which: (a) (i) a catalyst capable of creating a lactamate and (ii) a regulator chosen from the amides of formula R1—NH—CO—R2, in which R1 can be substituted with a radical R3—CO—NH— or R3—0— and in which R1, R2 and R3 denote an aryl, alkyl or cycloalkyl radical, are dissolved in the molten lactam; the temperature of this reaction mixture being between the melting point of the lactam and 15° C. higher in order to ensure its good stability, (b) the solution from step (a) is introduced into a mixing device and is then heated to a temperature which is sufficient to obtain bulk polymerization of the lactam in no more than 15 minutes. (b) is usually a continuous reactor, for example an extruder; however, it can be replaced with a mold.